Git: Unexpected Disconnect While Reading Sideband Packet

The "unexpected disconnect while reading sideband packet" error in Git typically occurs during push, fetch, or clone operations and indicates a network connectivity issue or Git configuration problem that prevents the complete transfer of data between your local repository and the remote server.

Problem Overview

The error manifests as:

Enumerating objects: 27, done.
Counting objects: 100% (27/27), done.
Delta compression using up to 16 threads
Compressing objects: 100% (24/24), done.
Writing objects: 100% (25/25), 187.79 KiB | 9.39 MiB/s, done.
Total 25 (delta 1), reused 0 (delta 0), pack-reused 0
send-pack: unexpected disconnect while reading sideband packet
fatal: the remote end hung up unexpectedly

This error can be frustrating because it often occurs intermittently, working fine one moment and failing the next, even with the same repository and network conditions.

Root Causes

Several factors can contribute to this error:

• Network instability or connectivity issues
• VPN connections with dynamic IP rotation
• Firewall, antivirus, or proxy interference
• Git configuration limitations
• Large files or repositories exceeding buffer sizes
• Outdated Git or SSH versions
• Server-side restrictions or authentication problems

Solutions

1. Network and Connectivity Checks

Before attempting complex solutions, rule out basic network issues:

Network troubleshooting steps

• Test your internet connection stability
• Disable VPNs (a common culprit, especially those with dynamic IP rotation)
• Check firewall and antivirus settings for interference
• Restart your router if experiencing intermittent connectivity

2. Git Configuration Adjustments

Increase Buffer Sizes

git config --global http.postBuffer 524288000  # 500MB buffer
git config --global core.compression 0         # Disable compression

WARNING

Increasing the postBuffer is only effective when the remote server has issues with chunked transfer encoding. It's not a universal fix and can significantly increase memory consumption.

Advanced Memory Configuration

Edit your global Git configuration (git config --global -e) and add:

[core] 
    packedGitLimit = 512m 
    packedGitWindowSize = 512m 
[pack] 
    deltaCacheSize = 2047m 
    packSizeLimit = 2047m 
    windowMemory = 2047m

3. SSH Configuration Optimization

For SSH connections, optimize your ~/.ssh/config:

Host *
  HostKeyAlgorithms ecdsa-sha2-nistp256,ssh-rsa
  ControlMaster auto
  ControlPath ~/.ssh/control:%h:%p:%r
  ControlPersist yes
  ServerAliveInterval 60
  Ciphers aes128-gcm@openssh.com

SSH vs HTTPS

If using HTTPS, consider switching to SSH:

git remote set-url origin git@github.com:username/repository.git

Or configure Git to use SSH by default:

git config --global url."git@github.com:".insteadOf "https://github.com/"

4. Debugging and Diagnostic Commands

Enable verbose output to identify the exact point of failure:

Linux/macOS

export GIT_TRACE_PACKET=1
export GIT_TRACE=1
export GIT_CURL_VERBOSE=1

Windows PowerShell

$env:GIT_TRACE_PACKET=1
$env:GIT_TRACE=1
$env:GIT_CURL_VERBOSE=1

Windows CMD

set GIT_TRACE_PACKET=1
set GIT_TRACE=1
set GIT_CURL_VERBOSE=1

5. Partial Clone Technique

For very large repositories, use a shallow clone followed by fetching the complete history:

git clone --depth 1 <repo_URI>
cd repository
git fetch --unshallow
git pull --all

6. Disable Delta Compression

If the issue is related to compression problems, disable delta compression:

git config --global pack.window 1

7. Update Software Components

Ensure you're using updated versions:

• Update Git to the latest version (especially important for Windows users)
• Update OpenSSH (Windows users should upgrade beyond version 9.2.2.0p1-Beta which fixed this issue)
• Use Git Desktop as an alternative client

8. Repository Maintenance

Clean up your local repository:

git fetch --prune
git branch -vv | grep -i 'gone' | awk '{print $1}' | xargs git branch -D
git fsck --full
git reflog expire --expire=now --all
git repack -a -d -l
git gc --prune=now --aggressive

Warning

These maintenance commands will remove your git stash contents and delete branches marked as gone. Use with caution.

9. Check for Large Files

Verify you're not pushing files that exceed GitHub's limits (100MB per file):

# Find large files in your repository
git rev-list --objects --all | git cat-file --batch-check='%(objecttype) %(objectname) %(objectsize) %(rest)' | awk '/^blob/ {print $4" "$3" "$2}' | sort -n -k 2 | tail -n 20

If large files are found, consider using Git LFS or removing them from your commit history.

Platform-Specific Solutions

Windows Users

• Upgrade OpenSSH to version 9.2.2.0p1-Beta or later
• Try using plink.exe instead of OpenSSH:

  $env:GIT_SSH="C:\ProgramData\chocolatey\bin\PLINK.EXE"

• For Windows 11 on ARM systems, use native ARM builds of Git

GitHub/GitLab Users

• Verify repository URL includes .git suffix
• Re-add SSH keys to your account
• Check for branch protection rules that might be causing issues
• Ensure email verification is complete if required

When All Else Fails

If none of the above solutions work:

1. Split large repositories into smaller ones
2. Use alternative clients like GitHub Desktop
3. Try from a different network to rule out ISP issues
4. Contact support for your Git hosting provider

Conclusion

The "unexpected disconnect while reading sideband packet" error typically stems from network issues or Git configuration limitations. Start with basic network troubleshooting, then progress through configuration adjustments, keeping your software updated, and finally consider repository restructuring if needed. Most cases can be resolved through a combination of buffer size increases, SSH optimization, and ensuring stable network conditions.